JPH04280520A - Alarm transfer device for optical relay system - Google Patents

Abstract

PURPOSE:To specify a fault location by detecting a fault at each block of optical relay, thereafter transferring the information to a reception station in the alarm transfer device of the optical relay system. CONSTITUTION:Optical transmission lines 2 are connected with each other by the amplifier circuit 11 in a repeater 1. The transmission side of the optical transmission line 2 is arranged with a reception station 3 and a transmission station 4. The repeater 1 is provided with the optical amplifier circuit 11 amplifying an optical signal through an optical fiber, an exciting light source 12 supplying an exciting light to the optical amplifier circuit 11 and a control circuit 13 controlling the exciting luminous intensity of the exciting light source 12 with an alarm signal based on the fault information of the optical transmission line 2. A reception station 3 separates the fault information from the received optical signal. Thus, a fault relating to the optical transmission line 2 is discriminated by the reception station 3.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alarm transfer device for an optical relay system. Specifically, it is an alarm transfer device for an optical relay system that uses optical fiber amplification to identify interruption of optical input in an optical relay system or a failure inside the relay device via an optical transmission line, and a relay device used for that purpose. , relating to terminal equipment.

In recent years, neodymium (
Optical fiber amplification using an optical fiber doped with rare elements such as Nd) and erbium (Er) as an amplification medium has been attracting attention. In particular, erbium ion (Er3+)
The optical fiber doped with has a laser transition frequency in the wavelength band of 1.55 μm. Therefore, optical amplification in this wavelength range is possible using a semiconductor laser as a pumping light source, and by applying an optical repeater using optical fiber amplification to an optical communication system, it is possible to easily improve the functionality and performance of the system. It is expected that

In addition to optical amplification repeaters, optical preamplifiers, optical booster amplifiers, and the like are also being considered as applications of optical fiber amplifiers to optical communication systems.

0004

[Background Art] Conventionally, optical communication systems using optical fibers have the characteristics that the optical fiber itself has low loss and wideband signal transmission characteristics, and also uses digital signal transmission to transmit various signals such as voice, data, and images. It has the characteristics that it is possible to combine and transmit. Therefore, when constructing communication systems such as long-distance submarine cables using optical fibers, it is expected to use optical amplifiers that are small and easy to handle. However, compared to land-based cables, submarine cables must satisfy strict external conditions such as high water pressure resistance and high tension, and once a failure occurs in the optical transmission line, it will cause problems in terms of cost and service. The impact is huge.

[0005] For this reason, optical relay systems such as submarine cables are required not only to have high reliability, but also to collect fault information in advance and reliably to take appropriate countermeasures. Conventionally, therefore, in optical repeating systems, loss changes in optical fibers are observed, or noise and code error rates are observed for each transmission section between repeaters, and the information is received as failure information from each repeater on the optical transmission line. It is sent to the station. In this case, since the optical signal input to the repeater is once converted to an electrical signal and electrically amplified, it is easy to synchronize it with the main signal that should be transmitted and perform frame regeneration. It was possible to send multiple pieces of fault information into the optical transmission line as bit signals other than the main signal.

[0006]

[Problem to be solved by the invention] By the way, when a relay system using optical amplification is adopted, the relay equipment directly amplifies and transmits the transmission information in the form of light without converting it into an electrical signal. Therefore, it is possible to extend the relay interval and simplify the repeater. Generally, a basic optical fiber amplifier consists of a pumping semiconductor laser, a fiber coupler, a non-polarized optical isolator, an erbium-doped fiber, and an optical bandpass filter. When a signal light equal to the energy difference between the population inversion levels formed in the erbium-doped fiber is incident, the signal light is amplified by stimulated emission from the fiber excited by the stimulation of the resonant frequency of the incident light. . This emitted signal light has the advantage of having an intensity proportional to the incident light and also having the same frequency and phase. However, on the other hand, it is not possible to process the information relayed via the optical fiber amplifier bit by bit and insert alarm information therein.

[0007] Therefore, in a relay system using such an optical amplifying means, it is not possible to add information for transmitting a warning to a transmitted signal and transmit it to a receiving station. Therefore, it is not easy to identify the interruption of optical input in an optical repeater system using optical fiber amplification or a fault inside the repeater equipment at the terminal equipment such as the receiving station, which causes problems in maintenance and inspection. there were.

[0008] The present invention has been made in view of these points, and after detecting a fault in each section of an optical relay in a relay device, the information is transferred to a terminal device such as a receiving station to identify the location of the fault. An object of the present invention is to provide an alarm transfer device for an optical relay system that is capable of identifying.

[0009]

SUMMARY OF THE INVENTION FIG. 1 is a block diagram illustrating the principle of the present invention that achieves the above object. In FIG. 1, a repeater 1 connects an optical transmission line 2 through an optical amplifier circuit 11. As shown in FIG. A receiving station 3 and a transmitting station 4 are arranged on the transmitting side of this optical transmission line 2.

This repeater 1 includes an optical amplifier circuit 11 that amplifies an optical signal through an optical fiber, a pump light source 12 that supplies pump light to the optical amplifier circuit 11, and an alarm signal based on failure information of the optical transmission line 2. The control circuit 13 controls the excitation light intensity of the excitation light source 12.

[0011]

[Operation] Fault information on the optical transmission line 2 is detected by the fault detection means 14, etc., and is inputted to the control circuit 13 as an alarm signal. Low frequency modulation is applied to the optical input to the relay device 1 using an alarm signal based on this fault information, and the fault information is superimposed on the optical signal and sent to the receiving station 3 side.

[0012] The receiving station 3 separates the above fault information from the received optical signal. This allows the reception station 3 to determine a failure regarding the optical transmission line 2.

[0013]

Embodiment FIG. 2 is a block diagram showing an example of the relay device 1 of the present invention. The optical fiber amplifier circuit 20 includes a branch circuit 2
The optical transmission line 2 is connected to the optical transmission line 2 via the optical fiber 1, and amplifies an input optical signal at a transmission rate of, for example, about 2.5 Gbit/sec. In the branch circuit 21, an optical signal proportional to the intensity of the input optical signal is extracted.

The opto-electric conversion circuit (O/E) 22 outputs an electric signal corresponding to the intensity of the input optical signal to the input level detection circuit 23. The input level detection circuit 23 generates fault information of a specific frequency (f1) when a fault such as a disconnection of the optical transmission line 2 or a transmission abnormality is detected from the electrical signal corresponding to the intensity of the optical signal. .

The optical fiber amplification circuit 20 performs optical fiber amplification using an erbium-doped fiber 24, a multiplexing circuit 25, and a pumping laser diode (LD) 26. Furthermore, the laser diode (LD) 26 is equipped with a photoelectric conversion circuit (O/E) to detect its luminous efficiency.
)27 are connected.

The output level detection circuit 28 has a failure detection function based on the output of the opto-electric conversion circuit (O/E) 27, and detects a failure in the optical amplification function such as power down of the optical fiber amplification circuit 20. In this case, fault information of a specific frequency (f2) is generated.

The output modulation control circuit 29 supplies a predetermined current to the laser diode (LD) 26 to cause it to emit light as an excitation light source for the optical fiber amplifier circuit 20. In this output modulation control circuit 29, when controlling the pumping light intensity of the laser diode (LD) 26, failure information of the optical transmission line 2 and failure information of the optical amplification function based on a failure of the repeater itself is input. If a laser diode (LD)
) 26 is modulated with a low frequency signal. That is, in the control circuit 29, a bias signal for causing the laser diode (LD) 26 to emit light is modulated by low frequency signals of frequencies f1 and f2 respectively assigned to the fault information, and is input to the multiplexing circuit 25. A low-frequency alarm signal is superimposed on the optical signal.

FIG. 3 is a time chart illustrating the optical signal waveform on which the alarm signal is superimposed. FIG. 3A shows an example of a transmission pulse signal input to the optical fiber amplifier circuit 20. In FIG. The relay device 1 shown in FIG. 2 is an optical transmission line 2
A plurality of alarm signals with frequency f1 are inserted into the control circuit 29 to compensate for the attenuation in each section of the optical signal transmitted from the transmitting station 4, and when the optical input of the repeater 1 goes down, an alarm signal of frequency f1 is sent to the control circuit 29. formed by. FIG. 3(b) shows an example of such an alarm signal.

This alarm signal applies intensity modulation to the main bias current value for amplifying the optical signal, and as a result, a low frequency modulated pulse signal as shown in FIG. 3(c) is transmitted through the optical fiber amplification. The signal is sent from the circuit 20 to the next transmission path. The alarm signal is superimposed on the optical signal at a different frequency depending on the fault information, and if multiple repeaters are present on the transmission path, a different frequency alarm signal is set for each repeater. . Furthermore, although it is assumed that multiple failures do not occur simultaneously, if the probability cannot be ignored, it is also possible to set a frequency that corresponds to a combination of failures that occur simultaneously.

FIG. 4 is a block diagram showing the configuration of the terminal equipment that constitutes the receiving station 3. As shown in FIG. In the receiving terminal device, a plurality of band pass filters BPF1,
It has BPF2, BPF3, and BPF4, and extracts an alarm signal from the pulse signal transmitted through the optical transmission line 2. That is, opto-electrical conversion circuit (O/E)
31, a high-pass filter (HPF) 32 extracts the transmission pulse signal received by the terminal device, and a signal regeneration circuit 33 regenerates the transmitted signal. BPF1, BP
F2, BPF3, and BPF4 extract a low frequency signal corresponding to the corresponding alarm signal from the output of the opto-electric conversion circuit (O/E) 31 converted into an electric signal, and send the alarm signal to the fault information detection circuit 34. Let us know if it is present or not. Fault information detection circuit 3
4, the fault information corresponding to the alarm signal is output as fault A1 if the power is down in relay device A, or as fault B2 if the optical input of relay device B is down.

In FIG. 4, a plurality of bandpass filters BP
Although the alarm signals extracted via F1, BPF2, BPF3, and BPF4 are shown as corresponding to fault information, one alarm signal can also correspond to a plurality of faults.

[0022] In the above explanation, a fault in an optical transmission line is superimposed on an optical signal being transmitted there, but in general, an optical signal cable constitutes a transmission line consisting of bidirectional optical fibers. Therefore, detected fault information can be superimposed on the optical signal on the transmission path in the opposite direction and sent back to the transmitting end station. In addition, in the above embodiment, a plurality of pieces of fault information are assigned to alarm signals of different frequencies, but a coded code that distinguishes the fault information is prepared, and a pulse with a frequency lower than the repetition frequency of the optical pulse is assigned. It may also be sent out to a transmission path.

[0023]

[Effects of the Invention] As explained above, in the present invention, an optical signal sent to a repeating device is loaded with an alarm signal based on failure information on an optical transmission line, and is transmitted to a receiving station or a transmitting station via an optical transmission line. can do. Therefore, when using a small and easy-to-handle optical amplifier, it is possible to easily and reliably collect failure information in optical relay systems such as submarine cables that require high reliability, and take appropriate measures. . Furthermore, it is possible to extend the relay interval in an optical relay system and simplify the repeater.

[Brief explanation of the drawing]

FIG. 1 is a block diagram illustrating the principle of the present invention.

FIG. 2 is a block diagram showing an example of the relay device 1 of the present invention.

FIG. 3 is a time chart illustrating an optical signal waveform on which an alarm signal is superimposed.

FIG. 4 is a block diagram showing the configuration of a terminal device.

[Explanation of symbols]

1 Relay device 2 Optical transmission line 3 Receiving station 11 Optical amplifier circuit 12 Excitation light source 13 Control circuit

Claims (3)

[Claims] [Claim 1] Optical transmission line (2) including a repeater (1)
a fault detection means (14) for detecting fault information of the relay device (1); and low frequency modulation is applied to the optical input to the relay device (1) by an alarm signal based on the fault information, and the fault information is superimposed on the optical signal. Control circuit (13) sending to receiving station (3) side
and a fault determination means for separating the fault information from the optical signal at the receiving station (3) and determining a fault in the optical transmission line (2). Device. 2. An optical amplifier circuit (11) that amplifies an optical signal through an optical fiber, a pumping light source (12) that supplies pumping light to the optical amplifier circuit (11), and failure information of the optical transmission line (2). A relay device for an optical relay system, comprising: a control circuit (13) that controls the excitation light intensity of the excitation light source (12) using an alarm signal based on the above. 3. Signal extracting means (BPF1 to BPF4) for extracting an alarm signal transmitted at a different frequency for each optical signal repeating device from the optical signal;
- 4) A terminal station device for an optical relay system, comprising: failure information detection means (34) for determining failure information of the relay device based on the alarm signal extracted in steps 4) to 4).